diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index aea3af9..abf6b0b 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -573,6 +573,33 @@
   if (!Opts.ProfileInstrumentUsePath.empty())
     setPGOUseInstrumentor(Opts, Opts.ProfileInstrumentUsePath);
 
+  if (Arg *A = Args.getLastArg(OPT_fclang_abi_compat_EQ)) {
+    Opts.setClangABICompat(CodeGenOptions::ClangABI::Latest);
+
+    StringRef Ver = A->getValue();
+    std::pair<StringRef, StringRef> VerParts = Ver.split('.');
+    unsigned Major, Minor = 0;
+
+    // Check the version number is valid: either 3.x (0 <= x <= 9) or
+    // y or y.0 (4 <= y <= current version).
+    if (!VerParts.first.startswith("0") &&
+        !VerParts.first.getAsInteger(10, Major) &&
+        3 <= Major && Major <= CLANG_VERSION_MAJOR &&
+        (Major == 3 ? VerParts.second.size() == 1 &&
+                      !VerParts.second.getAsInteger(10, Minor)
+                    : VerParts.first.size() == Ver.size() ||
+                      VerParts.second == "0")) {
+      // Got a valid version number.
+      if (Major == 3 && Minor <= 8)
+        Opts.setClangABICompat(CodeGenOptions::ClangABI::Ver3_8);
+      else if (Major <= 4)
+        Opts.setClangABICompat(CodeGenOptions::ClangABI::Ver4);
+    } else if (Ver != "latest") {
+      Diags.Report(diag::err_drv_invalid_value)
+          << A->getAsString(Args) << A->getValue();
+    }
+  }
+
   Opts.CoverageMapping =
       Args.hasFlag(OPT_fcoverage_mapping, OPT_fno_coverage_mapping, false);
   Opts.DumpCoverageMapping = Args.hasArg(OPT_dump_coverage_mapping);